This invention relates to a system and method for predicting the path of a motor vehicle during driving.
Many modern vehicles include safety systems which are intended to be activated before the occurrence of a hazardous event such as a collision or the departure of the vehicle from a road. However, it is strongly preferred not to activate vehicle safety systems unnecessarily, as this may be annoying and distracting for the driver, and may even result in hazard and injury, for instance in the case of an incorrect firing of an airbag inside the vehicle cabin.
In order to activate preemptive safety systems of this type, it is important to be able to determine the future path of the vehicle accurately. Predicting the future path of the vehicle will allow the vehicle's processor to determine whether or not a hazardous situation is generally likely to occur.
US2006/0085131 discloses a path estimation system in which a processor generates potential future paths based on different criteria, and assigns confidence levels to these different paths. A final predicted path is calculated based on a weighted combination of some or all of these potential paths. It is an object of the present invention to provide an improved path prediction system and method of this type.
Accordingly, one aspect of the present invention provides a method of predicting a future path of a vehicle, comprising the steps of: sensing a speed, and direction, and yaw rate of the vehicle; sensing a steering angle of the vehicle; sensing a driving lane near the vehicle, or along which the vehicle is being driven; calculating a first path prediction, for a first period of time following the current time, the first path prediction comprising a trajectory predicted based on the sensed speed and the direction and the yaw rate; calculating a second path prediction, for a second period of time, at least some of which is later than the first period of time, which assumes that a steering action arising from changes in the steering angle will take effect on the vehicle; calculating a third path prediction, for a third period of time, at least some of which is later than the second period of time, which assumes that the driver of the vehicle will control the trajectory of the vehicle to attempt to follow at least substantially the driving lane; and formulating a combined predicted path for the first, second and third periods of time, wherein the first, second and third path predictions each contribute to the combined predicted path.
Advantageously, the first, second and third path predictions each contribute to the combined predicted path with respective first, second and third contribution weights that vary over the time of the combined predicted path.
Preferably, in formulating the combined path prediction, the first path prediction only is used for the first period of time, and/or wherein, in formulating the combined path prediction, the second path prediction only is used for the second period of time, and/or wherein, in formulating the combined path prediction, the third path prediction only is used for the third period of time.
Conveniently, the first path prediction comprises the vehicle                a) continuing in the current sensed direction, or        b) continuing to turn with respect to the sensed direction at the sensed yaw rate, or        c) continuing to turn with respect to the sensed direction at a yaw rate which continues to change at the sensed rate of change of yaw rate, and        a) continuing at the current sensed speed, or        b) continuing to accelerate/decelerate with respect to the sensed speed at the sensed rate of acceleration/deceleration, or        c) continuing to accelerate/decelerate with respect to the sensed speed at an acceleration/deceleration which continues to change at the sensed rate of change of acceleration/deceleration        
Advantageously, the second period of time is calculated to begin after a period corresponding to a steering lag of the vehicle, and/or wherein the third period of time is calculated to begin after the sum of a first period corresponding to a reaction time for the driver, and a second period corresponding to a steering lag of the vehicle.
Preferably, for at least one time within the first, second or third period of time, a path prediction is made based on a combination of two or more of the first, second and third path predictions.
Conveniently, in a first transition period, the combined path prediction is based on a combination of the first path prediction and the second path prediction, according to their respective contribution weights.
Advantageously, in a second transition period, the combined path prediction is based on a combination of the second path prediction and the third path prediction, according to their respective contribution weights.
Preferably, in a third transition period, the combined path prediction is based on a combination of the first, second and third path predictions, according to their respective contribution weights.
Conveniently, the contribution weights of the respective path predictions vary over time during the first, second or third transition period, as applicable.
Advantageously, the method further comprises the step of activating one or more vehicle safety systems if it is determined, based on the combined predicted path, that the vehicle will, or is likely to, encounter a hazardous situation.
Preferably, the method further comprises the step of detecting one or more objects in the vicinity of the vehicle, with which the vehicle might collide.
Conveniently, the method further comprises the step of identifying the normal direction of travel for the driving lane.
Another aspect of the present invention provides a computer program comprising computer program code adapted to carry out all of the steps of any of the above when the program is run on a computer.
A further aspect of the invention provides a computer program according to the above, embodied on a computer-readable medium.